Academic journal article Environmental Health Perspectives

High Pesticide Exposure Events and Olfactory Impairment among U.S. Farmers

Academic journal article Environmental Health Perspectives

High Pesticide Exposure Events and Olfactory Impairment among U.S. Farmers

Article excerpt


The human sense of smell decreases with age. Olfactory impairment (OI), or poor sense of smell, is an understudied public health problem among older adults. OI affects up to 25% of older U.S. adults overall, and the proportion may increase to more than 60% for those [greater than or equal to]80 y of age (Adams et al. 2017; Dong et al. 2017a; Murphy et al. 2002). OI adversely affects critical aspects of human functioning such as detecting environmental hazards (Santos et al. 2004), nutrition (Mattes and Cowart 1994), mood and behavior (Schiffman et al. 1995a, 1995b), sexuality (Bhutta 2007), emotional and physical well-being (Smeets et al. 2009), and quality of life (Croy et al. 2014). In older adults, OI also predicts both short-term (Devanand et al. 2015; Pinto et al. 2014; Wilson et al. 2011) and long-term mortality (Ekstrom et al. 2017; Schubert et al. 2017) even after accounting for dementia and other chronic diseases. More importantly, converging evidence suggests that OI is one of the earliest and most important prodromal symptoms for Parkinson's disease (PD) (Chen et al. 2017; Ross et al. 2008) and Alzheimer's disease (AD) (Wilson et al. 2009; Yaffe et al. 2017). If these connections involve shared risk factors (Dong et al. 2015, 2017b), OI research could have major implications for understanding the pathophysiology of early stages of neurodegeneration.

Few population-based studies have investigated potential risk factors for OI in older adults (Dong et al. 2017a; Murphy et al. 2002; Schubert et al. 2012). Except for higher prevalence with older age and male sex (Murphy et al. 2002), associations with other demographic and lifestyle factors and environmental exposures are largely unknown. Pesticides represent a common environmental exposure and may impair the human sense of smell by affecting peripheral olfactory structures (e.g., inflammation of nasal mucosa) as well as the central nervous system (e.g., PD- or AD- related neuropathology) (Doty 2015). However, little empirical evidence exists on pesticides and OI.

Acute high exposure to certain pesticides can have life-threatening neurotoxic effects within hours (Jett 2011; Kamel and Hoppin 2004; Vale and Lotti 2015) and may have lasting neurological deficits years later (Kamel and Hoppin 2004). We only know of one case report that documented olfactory dysfunction following high exposure to pesticide. Minutes after entering a poorly ventilated examination room treated by a pyrethrin-based insecticide for pest infestation, an Italian doctor developed nasal irritation and progressive loss of odor perception (Gobba and Abbacchini 2012). After days in the room, the doctor developed anosmia or a total loss of the sense of smell; the authors reported that anosmia persisted through the last clinical visit 3 y later and was therefore deemed permanent. In this study, we aimed to comprehensively examine reports of a high pesticide exposure event (HPEE), as a surrogate for acute high pesticide exposure, in relation to OI among farmers in the Agricultural Health Study (AHS). Specifically, we hypothesized that a) a history of HPEEs reported at AHS enrollment is associated with self-reported OI; and b) the strength of association may depend on the body parts exposed, promptness in washing with soap and water, and specific chemicals involved.


Study Population

The AHS is an ongoing prospective cohort study of licensed private pesticide applicators (hereafter referred to as farmers) from Iowa and North Carolina. Details about this cohort have been published elsewhere (Alavanja et al. 1996). Briefly, 52,394 farmers enrolled in the AHS in 1993-1997 at the time of their pesticide license renewals by completing a questionnaire that asked about lifetime use of pesticides, sociodemographic characteristics, and medical history. In addition, 44% (n = 22,916) of these farmers completed a take-home questionnaire that sought further details on pesticide exposure, including a history of HPEEs. …

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